U.S. patent application number 11/008227 was filed with the patent office on 2005-06-16 for liquid crystal projector.
Invention is credited to Aoto, Katsuhide, Iwasaki, Naoki, Kawaai, Satoru.
Application Number | 20050128368 11/008227 |
Document ID | / |
Family ID | 34650459 |
Filed Date | 2005-06-16 |
United States Patent
Application |
20050128368 |
Kind Code |
A1 |
Aoto, Katsuhide ; et
al. |
June 16, 2005 |
Liquid crystal projector
Abstract
A liquid crystal projector splits light from a light source into
three lights of three different primary colors, respectively,
through an optical system, enters the three lights into three
liquid crystal display panels corresponding to the three different
primary colors, respectively, combines the three lights reflected
from the three liquid crystal display panels using a prism, and
projects the combined three lights through a first lens onto a
screen. The liquid crystal projector is provided with two second
lenses each of which is disposed at a respective one of two
entrance sides of the prism on which the three reflected lights are
incident, and a combination of the two second lenses, the prism and
the first lens constitute a projection lens optical system which
projects the combined three lights onto the screen.
Inventors: |
Aoto, Katsuhide; (Chiba,
JP) ; Iwasaki, Naoki; (Mobara, JP) ; Kawaai,
Satoru; (Saitama, JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET
SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Family ID: |
34650459 |
Appl. No.: |
11/008227 |
Filed: |
December 10, 2004 |
Current U.S.
Class: |
349/5 ;
348/E9.027 |
Current CPC
Class: |
H04N 9/3105
20130101 |
Class at
Publication: |
349/005 |
International
Class: |
G02F 001/1335 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 10, 2003 |
JP |
2003-412173 |
Claims
What is claimed is:
1. A liquid crystal projector which splits light from a light
source into three lights of three different primary colors,
respectively, through an optical system, enters said three lights
into three liquid crystal display panels corresponding to said
three different primary colors, respectively, combines said three
lights reflected from said three liquid crystal display panels
using a prism, and projects said combined three lights through a
first lens onto a screen, wherein said liquid crystal projector is
provided with two second lenses each of which is disposed at a
respective one of two entrance sides of said prism on which said
three reflected lights are incident, and a combination of said two
second lenses, said prism and said first lens constitute a
projection lens optical system which projects said combined three
lights onto said screen.
2. A liquid crystal projector which splits light from a light
source into three lights of three different primary colors,
respectively, through an optical system, enters said three lights
into three liquid crystal display panels corresponding to said
three different primary colors, respectively, combines said three
lights reflected from said three liquid crystal display panels
using a prism, and projects said combined three lights through a
first lens onto a screen, wherein said optical system comprises: a
mirror which reflects a first light of a first one of said three
primary colors of said light from said light source, and transmits
therethrough second and third lights of second and third ones of
said three primary colors of said light from said light source; a
first optical component which enters said first light reflected
from said mirror into a first one of said three liquid crystal
display panels, and then directs said first light reflected from
said first one of said three liquid crystal display panels into
said prism; and a second optical component which enters said second
and third lights transmitted through said mirror into second and
third ones of said three liquid crystal display panels,
respectively, and then directs said second and third lights
reflected from said second and third ones of said three liquid
crystal display panels into said prism; and wherein said liquid
crystal projector is provided with a second lens disposed between
said first optical component and said prism, and a third lens
disposed between said second optical component and said prism, and
a combination of said second lens, said third lens, said prism and
said first lens constitute a projection lens optical system which
projects said combined three lights onto said screen.
3. A liquid crystal projector according to claim 2, wherein said
first optical component is a polarizing beam splitter, said second
optical component is a polarizing beam splitter, and said prism is
a dichroic prism.
4. A liquid crystal projector according to claim 2, wherein said
first optical component is a polarizing beam splitter, said second
optical component is a polarizing beam splitter, and said prism is
a polarizing beam splitter.
5. A liquid crystal projector according to claim 2, wherein said
first optical component is a wire grid polarizing beam splitter of
a mirror configuration, said second optical component is a wire
grid polarizing beam splitter of a mirror configuration, and said
prism is a dichroic prism.
6. A liquid crystal projector according to claim 2, wherein said
first optical component is a wire grid polarizing beam splitter of
a prism configuration, said second optical component is a wire grid
polarizing beam splitter of a prism configuration, and said prism
is a dichroic prism.
7. A liquid crystal projector according to claim 2, wherein said
first optical component is a wire grid polarizing beam splitter of
a mirror configuration, said second optical component is a wire
grid polarizing beam splitter of a mirror configuration, and said
prism is a wire grid polarizing beam splitter of a prism
configuration.
8. A liquid crystal projector according to claim 2, wherein said
first optical component is a wire grid polarizing beam splitter of
a prism configuration, said second optical component is a wire grid
polarizing beam splitter of a prism configuration, and said prism
is a wire grid polarizing beam splitter of a prism configuration.
Description
CLAIM OF PRIORITY
[0001] The present application claims priority from Japanese
application serial no. 2003-412173, filed on Dec. 10, 2003, the
content of which is hereby incorporated by reference into this
application.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a liquid crystal projector,
and in particular to a color liquid crystal projector having an
improved optical system.
[0003] The color liquid crystal projector is such that white light
from one light source is split into three lights of primary colors
of red (R), green (G) and blue (B), then the three lights of the
primary colors are entered into the red-color, green-color and
blue-color liquid crystal display panels, respectively, and then
the three lights of the primary colors reflected from the
respective liquid crystal display panels are recombined and are
projected onto a screen spaced by a distance from the liquid
crystal projector via a projection lens.
[0004] Conventionally, splitting of light from one light source
into plural color lights was performed by means of a polarizing
beam splitter or the like, combining of lights of plural colors was
performed by means of a dichroic prism or the like, and the lights
from the dichroic prism are projected onto a screen via a
projection lens (see Japanese Patent Application Laid-Open Nos.
2003-177467 and 2001-318426 publications, for example).
SUMMARY OF THE INVENTION
[0005] Since, in the liquid crystal projector of the
above-described configuration, a polarizing beam splitter and a
dichroic prism are disposed between the respective liquid crystal
display panels and a projection lens, a back focal length of the
projection lens needs to be selected to be great, and consequently,
there has been a problem in that the projection lens needs to
selected to be large in size. Further, a distance between the
liquid crystal projector and a screen needs to be made large
because of the great back focal length, and this has been
preventing the thickness of a rear projection type. TV receiver and
the like, for example, from being reduced.
[0006] The present invention has been made in view of the above,
and it is an object of the present invention to provide a liquid
crystal projector capable of reducing the size of the projection
lens and its back focal length at the same time.
[0007] The following will explain briefly the summary of
representative ones of the inventions disclosed in this
specification.
[0008] In accordance with an embodiment of the present invention,
there is provided a liquid crystal projector which splits light
from a light source into three lights of three different primary
colors, respectively, through an optical system, enters said three
lights into three liquid crystal display panels corresponding to
said three different primary colors, respectively, combines said
three lights reflected from said three liquid crystal display
panels using a prism, and projects said combined three lights
through a first lens onto a screen, wherein said liquid crystal
projector is provided with two second lenses each of which is
disposed at a respective one of two entrance sides of said prism on
which said three reflected lights are incident, and a combination
of said two second lenses, said prism and said first lens
constitute a projection lens optical system which projects said
combined three lights onto said screen.
[0009] In accordance with another embodiment of the present
invention, there is provided a liquid crystal projector which
splits light from a light source into three lights of three
different primary colors, respectively, through an optical system,
enters said three lights into three liquid crystal display panels
corresponding to said three different primary colors, respectively,
combines said three lights reflected from said three liquid crystal
display panels using a prism, and projects said combined three
lights through a first lens onto a screen, wherein said optical
system comprises: a mirror which reflects a first light of a first
one of said three primary colors of said light from said light
source, and transmits therethrough second and third lights of
second and third ones of said three primary colors of said light
from said light source; a first optical component which enters said
first light reflected from said mirror into a first one of said
three liquid crystal display panels, and then directs said first
light reflected from said first one of said three liquid crystal
display panels into said prism; and a second optical component
which enters said second and third lights transmitted through said
mirror into second and third ones of said three liquid crystal
display panels, respectively, and then directs said second and
third lights reflected from said second and third ones of said
three liquid crystal display panels into said prism; and wherein
said liquid crystal projector is provided with a second lens
disposed between said first optical component and said prism, and a
third lens disposed between said second optical component and said
prism, and a combination of said second lens, said third lens, said
prism and said first lens constitute a projection lens optical
system which projects said combined three lights onto said
screen.
[0010] The present invention is not limited to the above-described
configurations, but various changes and modifications can be made
without departing from the true spirit and scope of the present
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] In the accompanying drawings, in which like reference
numerals designate similar components throughout the figures, and
in which:
[0012] FIG. 1 illustrates a configuration of an embodiment of a
liquid crystal projector in accordance with the present invention
including optical paths therein;
[0013] FIG. 2(a) illustrates an optical path in a case in which a
green light from a green-color liquid crystal display panel passes
through a second polarizing beam splitter, and then is projected
onto a screen by a projection lens optical system in accordance
with an embodiment of the present invention;
[0014] FIG. 2(b) is an illustration similar to that of FIG. 2(a),
but illustrates an optical path in a case in which a second lens is
omitted from the configuration of FIG. 2(a);
[0015] FIG. 3(a) is a schematic plan view of an example of a wire
grid polarizing beam splitter of a mirror configuration;
[0016] FIG. 3(b) is a schematic cross-sectional view of the wire
grid polarizing beam splitter shown in FIG. 3(a), taken along line
III(b)-III(b);
[0017] FIG. 3(c) is a schematic cross-sectional view of the wire
grid polarizing beam splitter shown in FIG. 3(a), taken along line
III(c)-III(c);
[0018] FIG. 4 is a schematic perspective view of an example of a
wire grid polarizing beam splitter of a prism configuration;
and
[0019] FIG. 5 tabulates examples of various combinations of optical
components.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] An embodiment of the liquid crystal projector in accordance
with the present invention will be explained with reference to the
drawings.
[0021] FIG. 1 illustrates a configuration of an embodiment of the
liquid crystal projector in accordance with the present invention
including optical paths therein.
[0022] In a system of rectangular co-ordinates in FIG. 1, a
dichroic mirror 3 is spaced from a light source 1 in the positive x
direction with an illuminating optical system 2 interposed
therebetween. A mirror plane of the dichroic mirror 3 is oriented
at 45.degree. to the x axis.
[0023] A first polarizing beam splitter 4 is disposed adjacently to
the dichroic mirror 3 in the positive y direction with its
reflective interface oriented at -45.degree. to the x axis. A
blue-color liquid crystal display panel DB for a blue color display
is disposed adjacently to the first polarizing beam splitter 4 in
the negative x direction. The blue-color liquid crystal display
panel DB comprises an envelope formed of a pair of opposing
substrates, a liquid crystal layer sandwiched between said pair of
opposing substrates, and a large number of pixels arranged in a
matrix fashion in a plane parallel with the liquid crystal layer.
The respective pixels are configured such that the light
transmission of their liquid crystal material layers is controlled
based upon pixel signals externally applied to them. One of the
pair of opposing substrates is transparent, and the other of the
pair is comprised of a semiconductor substrate having miniature
electronic circuits fabricated on or within its
liquid-crystal-layer-side surface. Here, this blue-color liquid
crystal display panel DB is of the so-called reflective type, and
reflective films which double as electrodes are provided on the
liquid-crystal-layer-side surface of the semiconductor substrate
for the respective pixels. Light from the outside is reflected by
these reflective films, and then is emitted to the outside
again.
[0024] A second polarizing beam splitter 9 is disposed adjacently
to the dichroic mirror 3 in the positive x direction with its
reflective interface oriented at -45.degree. to the x axis.
Disposed adjacently to the second polarizing beam splitter 9 are a
first phase plate 6 on the dichroic-mirror 3 side of the second
polarizing beam splitter 9, a green-color liquid crystal display
panel DG for a green color display in the negative y direction, and
a red-color liquid crystal display panel DR for a red color display
in the positive x direction. Both the green-color liquid crystal
display panel DG and the red-color liquid crystal display panel DR
are of the same configuration as that of the blue-color liquid
crystal display panel DB, and they are driven in the same way as
the blue-color liquid crystal display panel DB to produce the same
images.
[0025] A dichroic prism 5 is disposed above the second polarizing
beam splitter 9 in the positive y direction with its reflective
interface oriented at 45.degree. to the x axis. A second phase
plate 10 is disposed between the second polarizing beam splitter 9
and the dichroic prism 5. Further, a lens 20 is disposed between
the second phase plate 10 and the dichroic prism 5, and a lens 30
is disposed between the first polarizing beam splitter 4 and the
dichroic prism 5. A projection lens 7 is disposed above the
dichroic prism 5 in the positive y direction.
[0026] Here, the lens 20, the lens 30, the dichroic prism 5 and the
projection lens 7 are combined to constitute a projection lens
optical system represented by a block indicated by broken lines in
FIG. 1. This projection lens optical system can be treated as an
optical system independent of other optical components such as the
first polarizing beam splitter 4 or the like, and its functions
will be explained subsequently.
[0027] In the liquid crystal projector having the above optical
system, light from the light source 1 entered into the illuminating
optical system 2 is collimated and produces so-called s-polarized
light having a homogenized distribution. The light from the
illuminating optical system 2 enters the dichroic mirror 3, then a
blue light LB of the light is reflected at 90.degree. from the x
axis, and the remainder of the light is transmitted. After having
changed its optical path, the blue light LB enters the first
polarizing beam splitter 4, then changes its optical path through
an angle of 90.degree. and enters the blue-color liquid crystal
display panel DB.
[0028] The reflected light from the blue-color liquid crystal
display panel DB passes through the first polarizing beam splitter
4, then passes through the lens 30, and enters the dichroic prism
5. The dichroic prism 5 is configured so as to change the optical
path of the blue light LB into a direction at an angle of
90.degree. with respect to the x axis, and to pass a red light LR
and a green light LG therethrough.
[0029] The blue light LB entered into the dichroic prism 5 is
directed toward the projection lens 7 by the dichroic prism 5, and
then is emitted as an emergent light from the liquid crystal
projector. The blue light LB emitted from the liquid crystal
projector is projected onto a screen 8 disposed at a distance from
the liquid crystal projector.
[0030] The yellow light having passed through the dichroic mirror 3
passes through the first phase plate 6, and is split into the green
light LG and the red light LR by the first phase plate 6. The first
phase plate 6 rotates the direction of polarization of wavelengths
in the region of red only through 90.degree..
[0031] The red light LR enters the second polarizing beam splitter
9, passes through it without appreciable changes, then enters the
red-color liquid crystal display panel DR, then is reflected by the
red-color liquid crystal display panel DR, and then enters the
second polarizing beam splitter 9 again.
[0032] The path of the red light LR modulated by the liquid crystal
of the red-color liquid crystal display panel DR is changed by an
angle of 90.degree. with respect to the x axis by the second
polarizing beam splitter 9, and then the direction of the
polarization of the red light LR is rotated through 90.degree. by
the second phase plate 10, and then the red light LR passes through
the lens 20, and then passes through the dichroic prism 5 without
appreciable changes. The red light LR having passed through the
dichroic prism 5 is combined with the already explained blue light
LB, and then is projected onto the screen 8 via the projection lens
7.
[0033] The green light LG passes through the first phase plate 6
without appreciable changes, then its path is changed by an angle
of -90.degree. with respect to the x axis by the second polarizing
beam splitter 9, then the green light LG enters the green color
liquid crystal display panel DG, then is reflected by the liquid
crystal display panel DG, and then enters the second polarizing
beam splitter 9. The green light LG reflected by the green color
liquid crystal display panel DG has been modulated by the green
color liquid crystal display panel DG, then passes through the
second polarizing beam splitter 9, then passes through the second
phase plate 10, passes through the lens 20, and passes through the
dichroic prism 5. The green light LG passing through the dichroic
prism 5 is combined with the already described blue and red lights
LB, LR, and then is projected onto the screen 8 via the projection
lens 7.
[0034] In the liquid crystal projector of the above configuration,
a combination of a first lens 30 through which the blue light
passes, the dichroic prism 5 and the projection lens 7, or a
combination of a second lens 20 through which the green and red
lights pass, the dichroic prism 5 and the projection lens 7 can be
treated as an optical system independent of other optical
components as described above, and each of the combinations will be
referred to as the projection lens optical system A.
[0035] FIG. 2(a) illustrates an optical path in a case in which the
green light from the green-color liquid crystal display panel DG,
for example, passes through the second polarizing beam splitter 9,
and then is projected onto the screen 8 by the projection lens
optical system A. The projection lens optical system A in this case
is represented as a single equivalent lens, but, as explained
above, it is comprised of the second lens 20, the dichroic prism 5
and the projection lens 7.
[0036] Although FIG. 2(b) is an illustration similar to that of
FIG. 2(a), for purposes of comparison FIG. 2(b) illustrates an
optical path in a case in which the second lens 20 is omitted. In
this case, the first lens 30 (not included in the configuration of
FIG. 2(a)) is also omitted.
[0037] In the case illustrated in FIG. 2(a), the second polarizing
beam splitter 9 is interposed between the projection lens optical
system A and the green-color liquid crystal display panel DG, but
the dichroic prism 5 is not interposed between them. The dichroic
prism 5 can be considered as part of the projection lens optical
system A because the second lens 20 is provided at the entrance
side of the dichroic prism 5 as explained above. This means that
the back focal length BF of the projection lens optical system A
can be selected to be approximate to the width of the second
polarizing beam splitter 9 regardless of the presence of the
dichroic prism 5.
[0038] On the other hand, in the case illustrated in FIG. 2(b),
because of the absence of the second lens 20 at the entrance side
of the dichroic prism 5, the second polarizing beam splitter 9 and
the dichroic prism 5 are interposed between the projection lens 7
and the green-color liquid crystal display panel DG, and
consequently, the back focal length BF' of the projection lens 7 is
approximate to the sum of the widths of the second polarizing beam
splitter 9 and the dichroic prism 5, and consequently, the back
focal length BF' needs to be selected to be greater than that in
the case illustrated in FIG. 2(a).
[0039] As explained above, the configurations of this embodiment
are capable of reducing the back focal length of the projection
lens optical system A, and consequently, this embodiment provides
an advantage that can reduces the size of the lens of the
projection lens optical system A. Since the magnifying power of the
projection lens optical system A is increased, this embodiment also
provides an advantage of making shorter a projection distance PF
between the projection lens optical system A and the screen 8 for
the screen 8 of the same size. This makes it possible to realize
the reduction of the thickness of a rear projection type TV
receiver, for example.
[0040] Further, while the configuration illustrated in FIG. 1
employs the optical components such as the first polarizing beam
splitter 4, the second polarizing beam splitter 9 and the dichroic
prism 5, a wire grid polarizing beam splitter of a mirror
configuration and a wire grid polarizing beam splitter of a prism
configuration can be employed as the optical components instead of
them, and in this case also the same advantages as those explained
above can be provided.
[0041] The configurations and functions of the respective optical
components are as follows:
[0042] Polarizing Beam Splitter (Hereinafter Sometimes Referred to
as PBS)
[0043] A polarizing beam splitter has a prism configuration, and
its beam splitting interface is comprised of a multilayer film. The
polarizing beam splitter has a function of reflecting an
s-polarized light and transmitting a p-polarized light. Its
polarizing beam splitting efficiency is highly dependent upon an
incidence angle of light, and is degraded as the incidence angle
becomes wider. Further, the polarizing beam splitter exhibits a
phenomenon of rotating the plane of polarization of obliquely
incident light.
[0044] Dichroic Prism
[0045] A dichroic prism has a prism configuration, and its beam
splitting interface is comprised of a multilayer film. The dichroic
prism has a function of reflecting light in a specified wavelength
range and transmitting light in other wavelength ranges.
[0046] Wire Grid Polarizing Beam Splitter of a Mirror
Configuration
[0047] FIG. 3(a) is a schematic plan view of an example of a wire
grid polarizing beam splitter of a mirror configuration, FIG. 3(b)
is a schematic cross-sectional view of the wire grid polarizing
beam splitter shown in FIG. 3(a), taken along line III(b)-III(b),
and FIG. 3(c) is a schematic cross-sectional view of the wire grid
polarizing beam splitter shown in FIG. 3(a), taken along line
III(c)-III(c). The wire grid polarizing beam splitter of a mirror
configuration has a planar mirror structure, and its beam splitting
surface is comprised of an aluminum film 52 evaporated on a
substrate 51 and patterned in the form of wires arranged with a
pitch much less than the wavelengths of light of the visible
spectrum.
[0048] The wire grid polarizing beam splitter may be of the type
having dimensions similar to those described in U.S. Pat. Nos.
6,243,199 B1 and 6,234,634B1 issued to Hansen et al. on Jun. 5,
2001 and May 22, 2001, respectively. These Hansen et al. patents
are incorporated by reference herein for the purpose of
disclosure.
[0049] U.S. Pat. No. 6,234,634 B1 discloses the following
dimensions for the configuration shown in FIG. 3(a).
[0050] The pitch p of the wire arrangement must fall under
approximately 0.21 .mu.m to produce a beam splitter which has
reasonable performance throughout the visible spectrum.
[0051] The wire thickness t must be between about 0.04 .mu.m and
0.5 .mu.m.
[0052] The ratio of the wire width w to the wire pitch p must fall
within the ranges of from approximately 0.3 to 0.76.
[0053] The wire grid polarizing beam splitter of the mirror
configuration has a function of reflecting an s-polarized light and
transmitting a p-polarized light. Its polarizing beam splitting
efficiency is less dependent upon an incidence angle of light, and
the wire grid polarizing beam splitter of the mirror configuration
does not exhibit a phenomenon of rotating the plane of polarization
of obliquely incident light.
[0054] Wire Grid Polarizing Beam Splitter of a Prism
Configuration
[0055] FIG. 4 is a schematic perspective view of an example of a
wire grid polarizing beam splitter of a prism configuration. This
type of the beam splitter includes a pair of prisms 53, 54 having
sandwiched therebetween a beam splitting interface 55 similar to
the beam splitting surface explained in connection with FIGS. 3(a)
to 3(c).
[0056] The wire grid polarizing beam splitter of the prism
configuration operates on a principle similar to that for the
above-explained wire grid polarizing beam splitter of the mirror
configuration, and has much the same function as that of the
above-explained wire grid polarizing beam splitter of the mirror
configuration. The reason for this configuration is that, in a case
where an inclined glass plate is interposed between a liquid
crystal display panel and a projection lens, aberration is
produced, and therefore the prism configuration is employed to
prevent occurrence of the aberration.
[0057] Examples of various combinations of the above-described
optical components are tabulated in FIG. 5. In this table,
COMPONENT 1 represents a component corresponding to the first
polarizing beam splitter 4 in FIG. 1, COMPONENT 2 represents a
component corresponding to the second polarizing beam splitter 9 in
FIG. 1, and COMPONENT 3 represents a component corresponding to the
dichroic prism 5 in FIG. 1. In the following the combinations
described in FIG. 5 will be explained. A COMBINATION labeled
"BASIC" in FIG. 5 corresponds to the combination illustrated in
FIG. 1.
[0058] COMBINATION 1
[0059] A polarizing beam splitter is used as COMPONENT 1, a
polarizing beam splitter is used as COMPONENT 2, and a polarizing
beam splitter is used as COMPONENT 3. In this case, light from a
liquid crystal display panel passes through two polarizing beam
splitters, and thereby the degree of polarization is improved, and
consequently, the contrast ratio provided by the optical system is
increased.
[0060] COMBINATION 2
[0061] A wire grid polarizing beam splitter of the mirror
configuration is used as COMPONENT 1, a wire grid polarizing beam
splitter of the mirror configuration is used as COMPONENT 2, and a
dichroic prism is used as COMPONENT 3. In this case, the wire grid
polarizing beam splitters of the mirror configuration are used as
both COMPONENT 1 and COMPONENT 2, and consequently, the contrast
ratio provided by the optical system is increased.
[0062] COMBINATION 3
[0063] A wire grid polarizing beam splitter of the prism
configuration is used as COMPONENT 1, a wire grid polarizing beam
splitter of the prism configuration is used as COMPONENT 2, and a
dichroic prism is used as COMPONENT 3. In this case, the wire grid
polarizing beam splitters of the prism configuration are used as
both COMPONENT 1 and COMPONENT 2, and consequently, the contrast
ratio provided by the optical system is increased, and astigmatism
is eliminated compared with COMBINATION 2.
[0064] COMBINATION 4
[0065] A wire grid polarizing beam splitter of the mirror
configuration is used as COMPONENT 1, a wire grid polarizing beam
splitter of the mirror configuration is used as COMPONENT 2, and a
wire grid polarizing beam splitter of the prism configuration is
used as COMPONENT 3. In this case, the wire grid polarizing beam
splitters of the prism configuration are used as both COMPONENT 1
and COMPONENT 2, and therefore the degree of polarization is
improved, and consequently, the contrast ratio provided by the
optical system is increased.
[0066] COMBINATION 5
[0067] A wire grid polarizing beam splitter of the prism
configuration is used as COMPONENT 1, a wire grid polarizing beam
splitter of the prism configuration is used as COMPONENT 2, and a
wire grid polarizing beam splitter of the prism configuration is
used as COMPONENT 3. In this case, and the contrast ratio provided
by the optical system is increased, and astigmatism is eliminated
compared with COMBINATION 4.
* * * * *